Among pieces of electronic equipment such as a laptop personal computer, there is electronic equipment attached to an extended device not only to add an extended function to the electronic equipment but also to enhance the cooling function of the electronic equipment. The electronic equipment includes a heat source such as a CPU (Central Processing Unit) (arithmetic processor) mounted inside a housing, a heat transfer unit such as a heat sink connected to the heat source to transmit heat generated by the heat source up to the vicinity of an exhaust port provided in the housing, and a blower fan for discharging the heat transmitted to the vicinity of the exhaust port to the outside of the housing together with air. Then, the heat generated by the heat source is transmitted up to the vicinity of the exhaust port, and discharged to the outside of the housing together with air. The extended device provides the housing with a cooling air passage that communicates with the exhaust port, and includes a blower fan facing the exhaust port and a heat transfer unit such as a heat sink that borders the bottom face of the electronic equipment attached to the extended device. When the electronic equipment is attached to the extended device, the exhaust port lies just below the heat source mounted in the electronic equipment, and the cooling air passage runs just below the heat transfer unit. Then, the air discharged from the exhaust port in such a state that the electronic equipment is attached to the extended device passes under the heat source mounted in the electronic equipment, under the heat transfer unit, and through the heat transfer unit that borders the bottom face of the electronic equipment attached to the extended device, and is discharged to the outside of the housing (for example, see Japanese patent application publication No. 2000-75960).
Further, among pieces of electronic equipment such as a tablet personal computer, there is proposed electronic equipment also usable as a laptop personal computer by being attached to an extended device to add an extended function to the electronic equipment. Thus, the electronic equipment can be used as a tablet personal computer independently, and by being attached to the extended device, the electronic equipment can be used as a laptop personal computer (for example, see Japanese patent application publication No. 2005-158013).